1. Field of the Invention
The present invention relates to a count processing scheme utilizing an image processing for counting moving objects such as pedestrians passing through a pathway, a corridor, or a doorway, automobiles passing through a road, or objects moving over a belt conveyer, etc., and more particularly to a scheme for directional counting of moving objects which counts the moving objects direction by direction stably.
2. Description of the Background Art
As a scheme for directional counting of moving objects utilizing an image processing, the following schemes are conventionally known.
(1) A scheme in which corresponding object images are identified in sequential frames of the dynamic image, and the counting is made according to a number of identified object images and their trajectories.
(2) A scheme in which two monitoring lines are provided in an image field, and the counting is made according to an order of changes in the pixel values of the object images passing over each line.
(3) A scheme in which the counting is made by a region counting and a shape analysis of moving object extraction results using a space-time image obtained from a single counting line, as disclosed in Japanese Patent Application Laid Open No. 4-120682 (1992).
However, these conventionally known schemes are associated with the following problems.
The count processing according to the above scheme (1) requires a complicated processing in order to make correspondences of the objects among a number of images, so that it is very difficult to realize a real time processing.
The count processing according to the above scheme (2) is a frequently utilized one which is based on a similar operation principle as a mechanical counting device or a counting device using photo-electric tubes. However, in this scheme, when the pedestrians are passing continuously, there arises a situation in which different pedestrians are present on two monitoring lines at the same time, in which case the pixel values for these two monitoring lines do not change in the same order as in a case of only one pedestrian passing over these two monitoring lines and the expected changes in the pixel values disappear to make it impossible to detect any order of changes in the pixel values, such that it becomes impossible to judge the moving directions of the pedestrians.
In addition, in order to judge a moving direction in this scheme, it is necessary to observe the changes in the pixel values for these two monitoring lines at three timings of a time at which the pedestrian is on one of the monitoring lines, a time at which the pedestrian is on both of the monitoring lines, and a time at which the pedestrian is on another one of the monitoring line, so that it requires a considerable time in judging a moving direction.
Moreover, the moving directions that can be judged in this scheme are limited to two types of moving in and moving out for example.
The count processing according to the above scheme (3) is a scheme in which a pathway is imaged from above by a camera at an angle, and a two dimensional space-time image is formed from pixels on a line obliquely crossing the pathway in the images by using a space axis and a time axis, and then a moving object image is extracted from the space-time image and a moving direction is judged from an inclination of the extracted moving object image, so that it has an advantage that it can count the moving objects at high speed by a relatively simple processing while also obtaining motion vectors.
However, at a location where the flow of pedestrians changes (such as a doorway of a hall or an exhibition room at which dispersion/contraction of the flow occurs), or at a location where the camera cannot be placed sufficiently above, an inclination of a moving object image does not necessarily indicate a passing direction of a pedestrian, so that this scheme is prone to errors in the moving direction judgement in such circumstances.
In addition, according to this scheme, it is also possible to detect a passing speed of a moving object from a size of an inclination of a moving object image in a case a passing direction can be judged, but when the moving objects have different sizes themselves, the detected passing speed may contain a large error.
Moreover, under a circumstance in which a passing direction cannot be judged, it is also impossible to detect a passing speed.
Thus, presently, only a few algorithms are available for directional counting based on an image recognition, and there has been no counting scheme which can be accurate even under an environment involving many moving objects and diverse moving directions.